Swift嵌套字典检索：根据系统编码前缀获取章节与系统名称

原字典结构 #

let ataChapter: [[String:String]:Dictionary] = [
    ["21":"Air Conditioning"] : [
        "21-31":"Pressure control and monitoring",
        "21-51":"Pack flow control",
        "21-52":"Air cooling system",
        "21-55":"Emergency ram air inlet",
        "21-61":"Pack temperature control",
        "21-63":"Cockpit and cabin temperature control"],
    ["22":"Autoflight"] : [
        "22-01":"Overhead panel",
        "22-05":"FMA",
        "22-10":"A/P and F/D",
        "22-30":"Autothrust",
        "22-83":"FMGC"]
]

需求实现 #

1. 根据编码前2位获取章节名称 #

提取编码前2位作为目标章节编码，遍历顶级字典的键（小型[String:String]字典），匹配到对应编码后返回章节名称：

func getChapterName(from code: String) -> String? {
    // 校验编码长度，提取前2位章节编码
    guard code.count >= 2 else { return nil }
    let targetChapterCode = String(code.prefix(2))
    
    // 遍历顶级字典匹配
    for (chapterEntry, _) in ataChapter {
        if let chapterCode = chapterEntry.keys.first, chapterCode == targetChapterCode {
            return chapterEntry.values.first
        }
    }
    return nil
}

// 调用示例
if let chapterName = getChapterName(from: "21-52-30A") {
    print(chapterName) // 输出：Air Conditioning
}

2. 根据编码前4位获取系统名称 #

提取编码前4位作为目标系统编码，遍历所有二级字典，匹配到对应编码后返回系统名称：

func getSystemName(from code: String) -> String? {
    // 校验编码长度，提取前4位系统编码
    guard code.count >= 4 else { return nil }
    let targetSystemCode = String(code.prefix(4))
    
    // 遍历二级字典匹配
    for (_, systemDictionary) in ataChapter {
        if let systemName = systemDictionary[targetSystemCode] as? String {
            return systemName
        }
    }
    return nil
}

// 调用示例
if let systemName = getSystemName(from: "21-52-30A") {
    print(systemName) // 输出：Air cooling system
}

结构优化建议 #

原顶级字典使用[String:String]作为键，遍历匹配效率较低。建议调整为更直观高效的结构，无需使用struct，只需拆分出章节名称映射和嵌套字典：

// 章节编码与名称的映射表
let chapterNames: [String: String] = [
    "21": "Air Conditioning",
    "22": "Autoflight"
]

// 优化后的嵌套字典
let ataChapterOptimized: [String: [String: String]] = [
    "21": [
        "21-31": "Pressure control and monitoring",
        "21-51": "Pack flow control",
        "21-52": "Air cooling system",
        "21-55": "Emergency ram air inlet",
        "21-61": "Pack temperature control",
        "21-63": "Cockpit and cabin temperature control"
    ],
    "22": [
        "22-01": "Overhead panel",
        "22-05": "FMA",
        "22-10": "A/P and F/D",
        "22-30": "Autothrust",
        "22-83": "FMGC"
    ]
]

优化后的匹配函数更简洁高效：

// 优化后的章节名称获取
func getChapterNameOptimized(from code: String) -> String? {
    guard code.count >= 2 else { return nil }
    let targetChapterCode = String(code.prefix(2))
    return chapterNames[targetChapterCode]
}

// 优化后的系统名称获取
func getSystemNameOptimized(from code: String) -> String? {
    guard code.count >= 4 else { return nil }
    let targetChapterCode = String(code.prefix(2))
    let targetSystemCode = String(code.prefix(4))
    return ataChapterOptimized[targetChapterCode]?[targetSystemCode]
}

内容的提问来源于stack exchange，提问作者ScoobyDooku